Air India — Book for business class but given economy class

We were told that the booking is not available for my son which was rebook on 5 August 2022 in business class as per the below mail from Airindia and they ask us to wait they tried but at last they ask him to board to economy class at last min. I payed from business class and was given economy class with 3 hour of mentally harassment and my family trip had turn to be nightmare. I except my business class refund and compensation for the harassment and making my trip as a worst travel experience of my family.